An apparatus is provided which is capable of detecting a selected gas in a sample with a sensitivity of less than one part per billion (10.sup.9) parts; that is, with a sensitivity in the range of parts per trillion (10.sup.12). Methods for detecting a selected gas in a sample with a sensitivity in the range of parts per trillion are also disclosed. The apparatus and methods provide for detection of a selected gas in amounts as low as 10 parts per trillion (10.sup.12).
The apparatus and methods disclosed herein provide means whereby a selected gas in a relatively large sample volume is concentrated into a relatively small volume. Substantially all the gas is recovered from the sample and is concentrated in a small volume of water.
Ordinarily, concentration of a sample also results in concentration of salts and other contaminants in the sample. The presence of such salts and contaminants, that is, any component that is not the sample carrier, such as water, or the gas of interest, in the sample creates ionic interferences in the detection of a selected gas of interest in the sample, thereby reducing the sensitivity with which the selected gas can be detected.
The present apparatus and methods, however, concentrate the selected gas of interest but substantially eliminate the ionic interference one would otherwise expect from concentration of the sample. By obviating ionic interference, the present apparatus and methods permit one to use conductivity to measure only the component of the sample that is of interest. Further, the sensitivity with which the component of interest is able to be detected is vastly enhanced. Typically, the sensitivity of detection is enhanced by about at least twenty (20) fold over that of an unconcentrated control. The high sensitivity of the present apparatus and methods provides detection of the component in amounts as small as 10 parts per trillion.